Method of preparing synthetic lubricants from alpha olefins



Patented May 8, 1951 METHOD OF PREPARING SYNTHETIC LUBRICANTS FROM ALPHAOLEFINS Francis M. Seger, Pitman, William E. Garwood,

Haddonfield,

and Alexander N. Sachanen,

Woodbury, N. 3., assignors to Socony-Vacuum Oil Company, Incorporated, acorporation of New York No Drawing. Application April 21, 1949,

Serial No. 88,908

9 Claims.

This invention has to do with synthetic lubricants and, moreparticularly, has to do with polymerization of certain olefins to form anovel class of synthetic lubricants.

As disclosed in copending application Serial N 0. 761,716, filed July17, 1947, by two of the present applicants, now abandoned in favor ofapplication Serial No. 104,932, filed July 15, 1943, now Patent No.2,500,166, it has been found that normal, alpha mono-oleiins containingfrom six to about twelve carbon atoms per molecule polymerize, in theabsence of a catalyst and under certain welldefined reaction conditions,to form synthetic lubricants. The lubricants so formed possess a highlydesirable combination of properties: low pour point, high viscosityindex and good stability. With regard to stability, however, theselubricants are characterized by the same degree of resistance tooxidation as the highly-refined Pennsylvania type lubricating oils. Asis well recognized in. the art, the latter oils are excellent lubricantsin most respects but, under the rigorous conditions to which they aresubjected in current internal combustion engines and the like, they donot possess ufilcient resistance to oxidation. This has led to thedevelopment of numerous materials, oxidation inhibitors or antioxidants,which are blended in the oils in minor amounts to inhibit oxidation.Yet, while these inhibitors are of considerable value in reduc'ing thedeleterious effects of oxidation upon Pennsylvania type lubricants andupon the aforesaid synthetic lubricants, they represent an added cost inthe production of the oils.

It has now been found that the aforesaid normal, alpha mono-olefinspolymerize, in the presence of a mercaptan or thiol, to form syntheticlubricants possessed of a substantially higher degree of oxidationstability as well as high viscosity index and low pour point. Theinvention comprises, therefore, the production of excellent syntheticlubricants by polymerization of a normal, alpha mono-olefin having fromsix to about twelve carbon atoms per molecule, at an elevatedtemperature from about 600 F. to about 750 F. in the presence of a minoramount, from about 0.001 to about 0.1 molar proportion (per molarproportion of olefin), of a thiol.

REACTANTS As indicated above, the mono-olefins of this invention includemonomeric normal or straightchain alpha, mono-olefin; and contain fromsix to about twelve carbon atoms per molecule. Such mono-olefins arenormally liquid at temperatures of the order of 20-25 C. Illustrative ofsuch olefins are: hexane-l, octene-l, decene-l, and dodecene-l, and thelike. Preferred of such olefins, however, are those having from eight totwelve carbon atoms per molecule, with decene-l 2 forming particularlyoutstanding synthetic lubricants. It will be clear from the foregoingexamples that an alpha olefin may also be referred to as a l-olefin.

Not only may the mono-olefins of the aforesaid character he usedindividually in this invention, but they may also be used in admixturewith each other. In addition, olefin mixtures containing a substantialproportion of such mono-olefins may be used. Preferred of such mixturesare those containing a major proportion of a l-olefin or of l-oleflns.Representative of such mixtures are those obtained by the cracking ofparafiin Waxes and other paraffin products, and those obtained from theFischer-Tropsch and related processes. These hydrocarbon mixtures maycontain, in addition to the l-olefin or l-olefins, such materials as:other olefins, parafiins, naphthenes and aromatics.

The mercaptan or thiol used herein may have an alkyl, aralkyl, alkenyl,aralkenyl, cycloalkyl, aryl, alkaryl, alkenylaryl, heterocyclic groupetc. attached to the characterizing -Sl-l group. Representative of suchthiols or mercaptans are the following: alkyl-methyl, ethyl, propyl,nbutyl, secondary butyl, isobutyl, hexyl, heptyl, octyl, dodecyl, etc.;aralkyl-benzyl, methyl benzyl. dimethyl benzyl and the like;alkenyl-vinyl, ally], octadecenyl, etc.; aralkenyl-cinnamyl, styryl,etc.; cycloalkyl-cyclopentyl, cyclohexyl, methyl cyclohexyl, methylcyclopentyl, etc. aryl-phenyl (thiophenol), naphthyl (thionaphthol),anthryl (thianthranol), etc.; alkaryl-tolyl, xylyl, methyl naphthyl,etc.; alkenylaryl-vinyl phenyl, allyl phenyl, etc.;heterocyclic-thiophenethiol, thianthrenethiol, benzthiophenethiol,pyridine thiol, etc. Thiophenethiol and its homologs', together withmethods for their preparation are described in copending applicationSerial No. 721,454, filed January 10, 1947 now Patent No. 2,515,242.

Derivatives or substituted thiols may also be used herein, typical ofwhich is mercapto ethanol. It will also be understood thatpolymercaptans or polythiols may be used. Illustrative of the latter isdithioglycol. The preferred thiols, however, are thiophenethiol,thiophenol, and n-butyl mercaptan.

REACTION CONDITIONS Polymerization of the aforesaid l-oleflns with thethiols is effected under critical conditions. Temperatures as low asabout 300 F. and as high as the cracking temperatures of the lubricantsformed, about 700 F., may be used. However, the temperature range ofabout 550 F. to about 650 F. is considered optimum in View of theunusually high degree of excellence of the lubricants formed under suchconditions.

Polymerization is generally complete in from one to twenty hours,preferably three to ten hours. It should be noted that reactiontemperatures and times are interrelated, with the higher temperaturesbeing used for the shorter reaction periods, and with the lowertemperatures being used for the longer reaction periods.

The quantity of thiol or mercaptan used during the polymerization is, asindicated above, a relatively small quantity. This is a criticalfeature, for the quantity of thiol should not fall 1 below about 0.001molar proportion and preferably not exceed about 0.1 molar proportion,for each molar proportion of l-olefin. When the quantity of thiol fallsbelow the minimum indicated, little or no improvement in oxidation 1stability is realized. Similarly, when the maximum quantity of thiol isexceeded, the lubricant product generally contains an excessive quantityof sulfur, which restricts its use. Lubricants of 4 desired length oftime. Thereafter, the bomb was cooled and discharged. It should be notedthat the reaction times, recited as Time, hours in Table I, representthe time intervals during which 5 the bomb was maintained at the desiredtemperature; and do not include the time intervals necessary to heat thebomb and its content to the desired temperature, and do not include thetime intervals necessary to cool the bomb 3 after heat to the bomb hasbeen discontinued.

Normally, about one and one-half hours are required to raise thetemperature of the bomb from 70 F. to about 600 F.; similarly, several(about eight to sixteen) hours are required fOr the bomb to cool to 70F. after being maintained at 600 F.

for five hours.

The reaction or polymerization products discharged from the bomb weretopped and filtered as indicated in the runs shown in Table I. To

the latter character, however, are particularly g distinguish thesynthetic lubricants from the advantageous as blending stocks formineral oils, such as Pennsylvania type oils, for they impart oxidationstability to the oils with which they are blended.

crude reaction products and distillate fractions thereof, the refinedoils are identified in Table I as residual oils. The latter termidentifies the oils from which unreacted materials and Pressures rangingfrom atmospheric to 1,000 products of intermediate boiling range havebeen It will be understood, of course, that thepoly- 3 merization isaided by providing mixing of the olefins and thiols. This may beprovided by using various agitating means which are well known in theart. At the polymerization or reacseparated.

All of the tests and analyses to which the residual oils in Table I weresubjected are well known standard tests. In this connection, it will be0 noted that the designation N. N. refers to the neutralization number,which is a measure of the acidity of the oil. The abbreviation K. V. at210 F., cs." is used to identify the kinematic viscosity (of theresidual oils) at 210 F., meastion conditions, the olefins and thiolsare mutally ured in centistokes.

soluble and homogeneity is readily attained.

Following the polymerization procedure, it is generally advisable totreat the reaction product to remove any unreacted thiol and anyrelatively low boiling sulfur-containing products. may be accomplishedby any of the conventional procedures for removing thiols or mercaptansfrom hydrocarbon mixtures. For example, aqueous alkali solutions may beused. So also may solutizer solutions. 4

EXAMPLES In order to illustrate the principles of this invention, theresults of a series of typical, and

By way of illustration, the procedure followed in run 8 (Table I) isprovided in detail. Decene-l, 280 parts by weight or two molarproportions, and thiophenethiol, three parts by weight or 0.026 mo- Thislar proportion, were charged to a stainless steel,

non-limitin p ly rizations are set forth in bomb to a distillation flaskand topped at a prestabular form in Table I below. These polymerizationswere carried out in a rocking-type bomb (American Instrument Co.). Anolefin and a thiol were charged to a bomb, the free space was swept withnitrogen, and the bomb was heated to the desired temperature for thesure of 8 mms. (Hg) to a maximum liquid temperature of 231 C. (448 F.).The residual oil, 86 parts by weight, was filtered through a thin coatof a diatomaceous earth filter aid, Super Filtrol, and the filtrate, 78parts by weight was analyzed.

TABLE I Reaction Conditions P t h Max. Run Olcfimc Charge MolesMcrcaptan Moles '1 i pI K'S0Si5.,g

POLYMERIZATION OF OLEFINS WITH THIOLS Octane-l 336 3 Thiophenethiol l 0.009 (352 10A 700 Octene-l 336 3 .do 5 0. (H3 052 10 1,000 Octeno-L. 3363 l 0. 009 650 10 750 Octcue'2.. 360 3 5 0. 043 652 10 S002-EthylhcXcne-l 366 o d0 .l l 0. 009 (345 NW; 800

2-Ethylhexene-1... 366 3 do 5 0. 043 052 10 850 Deccnc-L- 420 3 d0 50.043 501 10 200 Decene-l 280 2 do 3 0. 026 010 10 200 Decone- 420 3 do5 0. 043 635 10 Decene-l 420 3 (lo 5 0. 043 700 3 1,250 Decenc-l 420 .5.do 5 0. 043 750 3 2, 300

TABLE I-Continued Residual Oil After Treat- Run Olofinw Char e 1 e 7 r bParts by 8 yp V I N N Specific Color Per Cent Weight Yield 1 c CS OGravity (Lovibond) S POLYMERIZAlION OF OLEFINS WITH 'lHlOLS l. Octcnc lTopped 33 9.8 11.54 2.80 2. Octene l... ...do 32 9.4 11.61 2. 74 3..Octane-2... 21 6. 2 13.26 3.02 4..." Octene-2..... 26 7.6 13.79 3.01 5.2-Ethylhexenc 8 2.4 Insullicient Sample 6..." 2Ethy1hoXene-l... 13 3.810.99 3. 22 Decenc-l 12 2.8 14.93 3. 8"... Decene-l 86 30.4 6.917 2.019.... Deccned 217 51 7. 55 2. 21 10..-. Deccnc-l 59 13. 9 15. 78 3. 5611.... Decene1 31 7.3 30. 76 5.14

1 Overall yield, based on original charges.

2 First topped at atmospheric pressure to a maximum liquid tcnir eraturcof 200 0., then topped at pressure or l-4 mm. to a maximum liquidtemperature 011404200 U. Residue filtered through thin coat or SuperFiltrol.

1 Topped at pressure of l S mm. to a maximum liquid temperature of 23lC. Residue filtered through coat of Super Filtrol.

From the data in Table I, it will be seen in runs 1-5, that asubstantially larger yield of synthetic oil is obtained from octene-l (anormal, alpha mono-olefin) than from either octene-2 or Z-ethylhexene-l.The ocetene-2 used in runs 3 and 4 (as obtained from a commercialsource) contained an appreciable quantity of octene-1 and, therefore,the actual difference between the two octenes, -l and -2, is muchgreater than shown here. There is also a significant difference inviscosity indices of the residual oils, with the oils obtained fromoctene-l being markedly superior. It is also noteworthy that as thequantity of thiophenethiol is increased, the viscosity index of theresidual oil is decreased.

Runs 7il show the effect of temperature and time upon the polymerizationof decene-l in Dry air is passed through the sample of oil at a rate often liters per hour. The test tube is heated at 260 F. for forty hoursin an aluminum block bath. The results reported at the end of the testare: neutralization number (N. N.); per cent viscosity increase at 210F.; sludge and lacquer; lead weight loss (in milligrams); and appearanceof copper. The oil is compared with a reference oil of similar viscosityand is rated on the basis of viscosity increase, N. N. increase, sludgeand lead weight loss. A maximum of three demerits is assigned to eachfactor rated. The sum of the demerits for an oil is called the stabilitynumber and ranges from zero to twelve. The reference mineral oils,solvent-refined Pennsylvania oils, have a stability number of six toseven.

TABLE II Catalytic oxidation test N. igy- PerCent Sludge, r C Pb Loss,Stability 1 sv Vis. Inc. Tube Mg Number SAE 10W Pennsylvania Mincral 01116 12. 91 Nil...... 235 6or7 Decenc-l Polymer 10.1 12.96 126 0.....Bright Cu.. 303.9 6

PRODUCTS FROM REACTION or MERCAPTANS DURING POLYME RIZATION or OLEFINSRun8 0.5 2. 09 3.9 Nil Brown 26.5 0 RunQ 1.7 2.44 8.9 ...do.... GrayStain" 44.3 0

1 Averaged values.

the presence of thiophenethiol. The results reveal that time-temperatureconditions of ten hours at about 600 F. to three hours at 700 F. is mostadvantageous. It is apparent that at temperatures of about 500 F., yieldof oil is low and sulfur content of the oil is relatively high.Similarly, with a temperature of 750 F. and a reaction time of threehours, viscosity index is substantially lower than at 700 F. for thesame time period.

That the residual oils of this invention have excellent stability isshown by results of a catalytic oxidation test, the results being shownbelow in Table II. This oxidation test reveals the stability of oilstoward catalytic oxidation.

The test oil, 25 00s., is placed in a 200 x 25 mms. test tube with 15.6square inches of sand-blasted iron wire, 0.78 square inch of polishedcopper wire, 0.87 square inch of polished aluminum wire, and 0.16?square inch of polished lead plate.

The test data set forth in Table II clearly indicate the high degree ofstability which characterizes the oils contemplated herein; anddemonstrate their superiority in this regard over a Pennsylvania typemineral oil and a lubricant obtained by thermally polymerizing a normal,alpha mono-olefin, decene-l, in the absence of a thiol.

As will be evident from the data presented above in Tables I and II, thepolymerization products of this invention are highly desirablelubricants per se. They are also of considerable value as blendingagents for other lubricating oils. In view of the inherent stability ofthe synthetic oils, they impart stability to the oils with which theyare blended. So also, they impart desirable viscosity index (V. I.) andpour point characteristics to the oils in combination therewith, for, asindicated above, they have advantageous viscosity index and pour pointproperties. In short, the

synthetic oils find utility in upgrading other lubricants. Typical oilswith which the synthetic oils may be blended are mineral oils such asare normally used in internal combustion and turbine engines. When soblended, the synthetic oils may comprise the major proportion of thefinal blended oil, or may even comprise a minor proportion thereof. Forexample, although used only in the amounts of the order of one to tenper cent, the synthetic oils improve the stability of mineral oils, suchas SAE 10 and 20 Pennsylvania type oils.

One or more of the individual properties of the synthetic lubricants ofthis invention may be further improved by incorporating therewith asmall, but eifective amount, of an addition agent such as anantioxidant, a detergent, an extreme pressure agent, a foam suppressor,a viscosity index (V. I.) improver, etc. Antioxidants which may be usedare well-known in the art, and are generally characterized byphosphorus, sulfur, nitrogen, etc. content; representative of suchmaterials is a phosphorusand sulfur-containing reaction product ofpinene and P235. Typical detergents which may be so used are metal saltsof alkylsubstituted aromatic sulfonic or carboxylic acids, asillustrated by diwax benzene barium sulfonate and barium phenate, bariumsalt of a wax-substituted phenol carboxylic acid. Extreme pressureagents are well known; illustrating such materials are numerous chlorineand/or sulfur containing compositions, one such material being achlornaphtha xanthate. Silicones, such as dimethyl silicone, may be usedto illustrate foam suppressing compositions. Viscosity index improvingagents Which may be used are typified by polypropylenes,polyisobutylenes, polyacrylate esters, and the like.

Contemplated also as within the scope of this invention is a method oflubricating relatively moving surfaces by maintaining therebetween afilm consisting of any of the aforesaid oils.

We claim:

1. A method of preparation of a viscous oil characterized by low pourpoint, high viscosity index and high oxidation stability, whichcomprises: non-catalytically heating a hydrocarbon charge consistingessentially of a normal, alpha mono-olefin having from six to abouttwelve carbon atoms per molecule in the presence of a thiol,

the molar ratio of said thiol to said olefin being from about 0.001 toabout 0.1, at a temperature between about 300 F. and about 700 F.

2. The method of claim 1 wherein the temperature is maintained betweenabout 550 F. and about 650 F. for a period of time between about tenhours and about three hours, respectively.

3. The method of claim 1 wherein said molar ratio is from about 0.005 toabout 0.05.

4. The method of claim 1 wherein the monoolefin is a monomer having fromabout eight to about twelve carbon atoms per molecule.

5. The method of claim 1 wherein the thiol is an alkyl thiol.

6. The method of claim 1 wherein the thiol is an aryl thiol.

'7. The method of claim 1 wherein the thiol is a heterocyclic thiol.

8. The method of preparation of a viscous oil characterized by low pourpoint, high viscosity index and high oxidation stability, whichcomprises: non-catalytically heating a charge consisting essentially ofone molar proportion of n-decene-l and about 0.015 molar proportion ofthiophenethiol, at about 635 F. for about ten hours.

9. The method of preparation of a viscous oil characterized by low pourpoint, high viscosity index and high oxidation stability, whichcomprises: non-catalytically heating a charge consisting essentially ofone molar proportion of n-octene-l and about 0.003 molar proportion ofthiophenethiol, at about 650 F. for about ten hours.

FRANCIS M. SEGER. WILLIAM E. GARWOOD. ALEXANDER N. SACHANEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,258,806 Pier et a1. Oct. 14,1941 2,382,700 Eby Aug. 14, 1945 2,486,441 Seger et a1 Nov. 1, 1949OTHER REFERENCES Eglofi: The Reactions of Pure Hydrocarbons" (ReinholdPubl. Corp., 1937), pages 362-363.

1. A METHOD OF PREPARATION OF A VISCOUS OIL CHARACTERIZED BY LOW POURPOINT, HIGH VISCOSITY INDEX AND HIGH OXIDATION STABILITY, WHICHCOMPRISES: NON-CATALYTICALLY HEATING A HYDROCARBON CHARGE CONSISTINGESSENTIALLY OF A NORMAL, ALPHA MONO-OLEFIN HAVING FROM SIX TO ABOUTTWELVE CARBON ATOMS PER MOLECULE IN THE PRESENCE OF A THIOL, THE MOLARRATIO OF SAID THIOL TO SAID OLEFIN BEING FROM ABOUT 0.001 TO ABOUT 0.1,AT A TEMPERATURE BETWEEN ABOUT 300* F. AND ABOUT 700* F.